Editing Parasitoid (section)

===Evolutionary options===

A perspective on the evolutionary options can be gained by considering four questions: the effect on the [[Fitness (biology)|reproductive fitness]] of a parasite's hosts; the number of hosts they have per life stage; whether the host is prevented from reproducing; and whether the effect depends on intensity (number of parasites per host). From this analysis, proposed by K. D. Lafferty and A. M. Kunis, the major evolutionary strategies of parasitism emerge, alongside predation.<ref name=LaffertyKuris2002>{{cite journal |last1=Lafferty |first1=K. D. |last2=Kuris |first2=A. M. |date=2002 |title=Trophic strategies, animal diversity and body size |journal=Trends Ecol. Evol. |volume=17 |issue=11 |pages=507–513 |doi=10.1016/s0169-5347(02)02615-0}}</ref>

{| class="wikitable"
|+ Evolutionary strategies in parasitism and predation<ref name=LaffertyKuris2002/><br/>({{font color|green|intensity-dependent: green, roman}}<!--colour is used redundantly alongside position (above/below), indentation and font-->;<br/>&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;''{{font color|purple |intensity-independent: purple, italics}}'')
! Host fitness !! Single host, stays alive !! Single host, dies !! Multiple hosts
|-
| '''Able to<br/>reproduce<br/>(fitness > 0)''' || {{font color|green|Conventional parasite}}<br/>&nbsp;&nbsp;&nbsp;''{{font color|purple |Pathogen}}'' || {{font color|green|Trophically transmitted parasite}}{{efn|Trophically transmitted parasites are transmitted to their definitive host, a predator, when their intermediate host is eaten. These parasites often modify the behaviour of their intermediate hosts, causing them to behave in a way that makes them likely to be eaten, such as by climbing to a conspicuous point: this gets the parasites transmitted at the cost of the intermediate host's life.}}<br/>&nbsp;&nbsp;&nbsp;''{{font color|purple |Trophically transmitted pathogen}}'' || {{font color|green|Micropredator}}<br/>&nbsp;&nbsp;&nbsp;''{{font color|purple |Micropredator}}''
|-
| '''Unable to<br/>reproduce<br/>(fitness = 0)''' || {{font color|green| &mdash; }}<br/>&nbsp;&nbsp;&nbsp;''{{font color|purple |Parasitic castrator}}'' || {{font color|green|Trophically transmitted parasitic castrator}}<br/>&nbsp;&nbsp;&nbsp;''{{font color|purple | Parasitoid}}'' || {{font color|green|Social predator}}{{efn|The [[wolf]] is a social predator, hunting in packs; the [[cheetah]] is a solitary predator, hunting alone. Neither strategy is conventionally considered parasitic.}}<br/>&nbsp;&nbsp;&nbsp;''{{font color|purple |Solitary predator}}''
|}

Parasitoidism, in the view of [[Robert Poulin (zoologist)|R. Poulin]] and H. S. Randhawa, is one of six main [[evolutionary strategies]] within [[parasitism]], the others being [[parasitic castrator]], directly transmitted parasite, [[wikt:trophic|trophically]] transmitted parasite, [[vector (epidemiology)|vector]]-transmitted parasite, and micropredator. These are [[adaptive peaks]], with many possible intermediate strategies, but organisms in many different groups have consistently [[convergent evolution|converged]] on these six.<ref name=PoulinRandhawa2015>{{cite journal |last1=Poulin |first1=Robert |author1-link=Robert Poulin (zoologist) |last2=Randhawa |first2=Haseeb S. |title=Evolution of parasitism along convergent lines: from ecology to genomics |journal=Parasitology |date=February 2015 |volume=142 |issue=Supplement 1 |pages=S6–S15 |doi=10.1017/S0031182013001674 |pmc=4413784 |pmid=24229807}}</ref><ref name=Rollinson>{{cite book |author=Poulin, Robert |author-link=Robert Poulin (zoologist) |editor1=Rollinson, D. |editor2=Hay, S. I. |title=The Many Roads to Parasitism: A Tale of Convergence |journal=Advances in Parasitology |url=https://books.google.com/books?id=9y4AlXka7t0C&pg=PA28 |year=2011 |volume=74 |publisher=Academic Press |isbn=978-0-12-385897-9 |pages=27–28|doi=10.1016/B978-0-12-385897-9.00001-X |pmid=21295676 }}</ref>

Parasitoids feed on a living host which they eventually kill, typically before it can produce offspring, whereas conventional parasites usually do not kill their hosts, and predators typically kill their prey immediately.<ref name=Stevens2010>{{cite journal |last1=Stevens |first1=Alison N. P. |title=Predation, Herbivory, and Parasitism |journal=Nature Education Knowledge |date=2010 |volume=3 |issue=10 |page=36 |url=https://www.nature.com/scitable/knowledge/library/predation-herbivory-and-parasitism-13261134 |access-date=12 February 2018 |quote=Predation, herbivory, and parasitism exist along a continuum of severity in terms of the extent to which they negatively affect an organism's fitness. ... In most situations, parasites do not kill their hosts. An exception, however, occurs with parasitoids, which blur the line between parasitism and predation.}}</ref><ref>{{cite journal |last1=Møller |first1=A. P. |year=1990 |title=Effects of parasitism by a haematophagous mite on reproduction in the barn swallow |jstor=1938645 |journal=Ecology |volume=71 |issue=6 |pages=2345–2357 |doi=10.2307/1938645|bibcode=1990Ecol...71.2345M }}</ref>

<!--if reorganising, ensure anchors remain with following text-->
{{anchor|Koinobiont}}
{{anchor|Idiobiont}}